Reactions {reverse aldol condensation} {condensation reaction, carbohydrate} can lengthen carbon chains by two carbons.
ketol-enol
Proton can transfer from -CO-CH2OH ketol last carbon to next-to-last carbon, to make enol double bond between carbons and alcohol on next-to-last carbon: -COH=CHOH. Enol can add water molecule to make separated charges: -(H2OC+OH)-(C-HOH) [2 is subscript and + and - are superscripts]. Last carbon becomes negative, and next-to-last carbon becomes positive.
aldol
Enol with separated charges can attack aldol, -CHOH-CHO, carbonyl double bond to single-bond carbonyl carbon and carbanion: -CHOH-(C-OH)-CHOH-(H2OC+OH)- [2 is subscript and + and - are superscripts]. Positive charge is still on next-to-last enol carbon, and negative charge is on last aldol carbon.
proton transfer
Water leaves, and proton transfers from positive charge to carbanion and makes atoms neutral: -CHOH-CHOH-CHOH-CHOH-.
Physical Sciences>Chemistry>Biochemistry>Carbohydrate>Chemical Reaction
5-Chemistry-Biochemistry-Carbohydrate-Chemical Reaction
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Date Modified: 2022.0224